Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?


too_many_tools
 

I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the long storage period?

Thanks


Ed Breya
 

There are basically two schools of thought on that - one is to bring them up slowly with a variac and watch for any problems, and the other is to just plug them in and see what happens. I adhere to the latter philosophy, which has never disappointed me. You'll see valid arguments for both approaches - the archives have plenty.

The only preparation I'd recommend is that if you're in a high voltage country, to make sure the line selectors are set for 240V (high range), and (from recent discussions) if any of the AC power input filters are of Schaffner brand, to be prepared for possible failure of those parts.

Ed

--- In TekScopes@..., "too_many_tools" <too_many_tools@...> wrote:

I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the long storage period?

Thanks


Craig Sawyers <c.sawyers@...>
 

I have received a number of Tektronix oscilloscopes and logic analyzers
that
have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the
long
storage period?
Power supply capacitors will possible need to be re-formed, and may have (a)
dried out and have low capacitance/high ESR or (b) with twist-lock Sprague
they may have gone open circuit. Check the web for the ways to reform, and
the archives for other capacitor ailments. Depending on the series of the
scopes, tantalum bead capacitors used for local supply decoupling might
instantly and randomly go short circuit. And switch contacts will probably
be intermittent and need cleaning. Pots are likely to be noisy, and will
need the track re-lubricating - check the Tekscopes archive for various
creative ways of doing this!

Good luck! Tell us more about your haul....

Craig


 

On Wed, Jul 17, 2013 at 8:10 AM, too_many_tools
<too_many_tools@...> wrote:
I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the long storage period?

Thanks

First of all, open each unit, check for stuff like moths, dead rats,
snakes, cockroaches, spiders. A buggy unit can break when you power
on.

Then, store the units in a warm, dry room for several weeks. Let them
dry. They've probably been in a place that wasn't climate controlled,
and are full of moisture. You do NOT want to turn them on at once. Get
a hygrometer (moisture meter), measure the moisture in that room
before the units get put in, then leave them drying until the moisture
meter drops down to the original level.

Get a variac, run the Units on 10% voltage, then after half an hour on
20%, then after half an hour 50%, then after an hour 75%, then after
half an hour 85%, half an hour and then 100%. This should reform power
supply capacitors. The nice thing is that you can do this in parallel,
with all units at once. Just make sure you can pull each plug QUICKLY,
and that you don't mix the plugs up.

Cheers,
D.


vdonisa
 

Wear safety glasses, make sure you can cut off power quickly from a remote switch, have a CO2 fire extinguisher at hand.

Just kidding :-) or maybe not...

The variac thing can destroy some designs of power supply.

--- In TekScopes@..., "cheater00 ." <cheater00@...> wrote:

On Wed, Jul 17, 2013 at 8:10 AM, too_many_tools
<too_many_tools@...> wrote:
I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the long storage period?

Thanks

First of all, open each unit, check for stuff like moths, dead rats,
snakes, cockroaches, spiders. A buggy unit can break when you power
on.

Then, store the units in a warm, dry room for several weeks. Let them
dry. They've probably been in a place that wasn't climate controlled,
and are full of moisture. You do NOT want to turn them on at once. Get
a hygrometer (moisture meter), measure the moisture in that room
before the units get put in, then leave them drying until the moisture
meter drops down to the original level.

Get a variac, run the Units on 10% voltage, then after half an hour on
20%, then after half an hour 50%, then after an hour 75%, then after
half an hour 85%, half an hour and then 100%. This should reform power
supply capacitors. The nice thing is that you can do this in parallel,
with all units at once. Just make sure you can pull each plug QUICKLY,
and that you don't mix the plugs up.

Cheers,
D.


David DiGiacomo
 

On Wed, Jul 17, 2013 at 12:10 AM, too_many_tools
<too_many_tools@...> wrote:
I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the long storage period?
20 years is just not that long. You can plug them in and see if they
work. You'll probably want to check the batteries, if any, for
leakage. Hard to say specifically when you don't tell us what
equipment you are talking about.


Power supply capacitors will possible need to be re-formed...
I strongly disagree with this. We are not talking about breadboards
from 1930. Capacitors in logic analyzers do not need to be reformed
after 20 years. (And if they did, it would be a mistake to try to do
it in-circuit.)


Get a variac, run the Units on 10% voltage, then after half an hour on
20%, then after half an hour 50%, then after an hour 75%, then after
half an hour 85%, half an hour and then 100%.

ARGGHHH! I hate seeing misguided advice like this. Again, we are
not talking about an old tube radio. Do not do this to a Tek power
supply!


tubesnthings@aol.com <tubesnthings@...>
 

Sorry, but with regulated supplies there can only be one approach to power-up: flip the switch. Otherwise you risk exceeding current limits of psu components. If you're REALLY worried about the electrolytics, reform them first.
Bernd Schroder

Sent from my Verizon Wireless Droid


-----Original message-----
From: Ed Breya <edbreya@...>
To:
TekScopes@...
Sent:
Wed, Jul 17, 2013 07:17:06 GMT+00:00
Subject:
[TekScopes] Re: Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?

 

There are basically two schools of thought on that - one is to bring them up slowly with a variac and watch for any problems, and the other is to just plug them in and see what happens. I adhere to the latter philosophy, which has never disappointed me. You'll see valid arguments for both approaches - the archives have plenty.

The only preparation I'd recommend is that if you're in a high voltage country, to make sure the line selectors are set for 240V (high range), and (from recent discussions) if any of the AC power input filters are of Schaffner brand, to be prepared for possible failure of those parts.

Ed

--- In TekScopes@..., "too_many_tools" <too_many_tools@...> wrote:
>
> I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.
>
> I have yet to apply power to them.
>
> What preparation if any should I do to them before applying power?
>
> Afterwards, what possible problems should I look for in them after the long storage period?
>
> Thanks
>


tubesnthings@aol.com <tubesnthings@...>
 


Do NOT use a variac on equipment with regulated supplies!!!!
You will likely exceed current limits of regulator components!!!!!!!!!
Bernd Schroder

Sent from my Verizon Wireless Droid


-----Original message-----
From: "cheater00 ." <cheater00@...>
To:
TekScopes@...
Sent:
Wed, Jul 17, 2013 10:15:32 GMT+00:00
Subject:
Re: [TekScopes] Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?

 

On Wed, Jul 17, 2013 at 8:10 AM, too_many_tools
<too_many_tools@...> wrote:
> I have received a number of Tektronix oscilloscopes and logic analyzers that have been stored unpowered for over 20 years.
>
> I have yet to apply power to them.
>
> What preparation if any should I do to them before applying power?
>
> Afterwards, what possible problems should I look for in them after the long storage period?
>
> Thanks

First of all, open each unit, check for stuff like moths, dead rats,
snakes, cockroaches, spiders. A buggy unit can break when you power
on.

Then, store the units in a warm, dry room for several weeks. Let them
dry. They've probably been in a place that wasn't climate controlled,
and are full of moisture. You do NOT want to turn them on at once. Get
a hygrometer (moisture meter), measure the moisture in that room
before the units get put in, then leave them drying until the moisture
meter drops down to the original level.

Get a variac, run the Units on 10% voltage, then after half an hour on
20%, then after half an hour 50%, then after an hour 75%, then after
half an hour 85%, half an hour and then 100%. This should reform power
supply capacitors. The nice thing is that you can do this in parallel,
with all units at once. Just make sure you can pull each plug QUICKLY,
and that you don't mix the plugs up.

Cheers,
D.


Ed Breya
 

Sorry, but I have to disagree with your disagreement, even though I never use a variac - I just plug stuff in and go.

Most electrical and electronic equipment is (or should be) designed to withstand any possible line condition, which can include going from nothing to too much, over various time ranges. With linear supplies, the outputs will just be too low and out of regulation if line voltage is too low. Switching supplies usually have UV lockout, so won't start if the line is too low. Small AC motors usually are "impedance protected," while large ones tend to have overload protection devices to disconnect a locked rotor fault. Any equipment that relies on sequencing or presence of certain internal supplies for proper and safe operation should be designed with appropriate interlocks and protection against this type of failure.

A lot can happen to line voltage, from brownouts and having too long or too light of an extension cord at one extreme, to high-line conditions and surges at the other - and most stuff survives it within reason. The equipment of course won't necessarily work properly, but it should be OK for the duration of someone gradually turning up a variac and watching for problems for a few seconds.

Ed

--- In TekScopes@..., "tubesnthings@..."<tubesnthings@...> wrote:

Sorry, but with regulated supplies there can only be one approach to
power-up: flip the switch. Otherwise you risk exceeding current limits of
psu components. If you're REALLY worried about the electrolytics, reform
them first.
Bernd Schroder

Sent from my Verizon Wireless Droid

-----Original message-----
From: Ed Breya <edbreya@...>
To: TekScopes@...
Sent: Wed, Jul 17, 2013 07:17:06 GMT+00:00
Subject: [TekScopes] Re: Reviving Tek Equipment After 20 Years In
Storage...What to Do and Look For?

There are basically two schools of thought on that - one is to bring them up
slowly with a variac and watch for any problems, and the other is to just
plug them in and see what happens. I adhere to the latter philosophy, which
has never disappointed me. You'll see valid arguments for both approaches -
the archives have plenty.

The only preparation I'd recommend is that if you're in a high voltage
country, to make sure the line selectors are set for 240V (high range), and
(from recent discussions) if any of the AC power input filters are of
Schaffner brand, to be prepared for possible failure of those parts.

Ed

--- In TekScopes@..., "too_many_tools" <too_many_tools@>
wrote:

I have received a number of Tektronix oscilloscopes and logic analyzers
that have been stored unpowered for over 20 years.

I have yet to apply power to them.

What preparation if any should I do to them before applying power?

Afterwards, what possible problems should I look for in them after the
long storage period?

Thanks


Craig Sawyers <c.sawyers@...>
 

Most electrical and electronic equipment is (or should be) designed to
withstand any possible line condition, which can include going from
nothing
to too much, over various time ranges. With linear supplies, the outputs
will
just be too low and out of regulation if line voltage is too low.
Switching
supplies usually have UV lockout, so won't start if the line is too low.
Small AC
motors usually are "impedance protected," while large ones tend to have
overload protection devices to disconnect a locked rotor fault. Any
equipment that relies on sequencing or presence of certain internal
supplies
for proper and safe operation should be designed with appropriate
interlocks
and protection against this type of failure.
I'd agree for the equipment when new. But (although we don't know what this
equipment is) if this has been in storage for 20 years it is most likely 40
years old or more. So possibly has a few issues.

But like you, I just put the power on and let rip. Never used a variac to
power up stuff, even with the infamous high efficiency power supply in tick
mode on a dummy load.

Craig


Ed Breya
 

Yup, I know what you mean. The last time I needed to use a variac was to diagnose a 7904 with a shorted main DC filter cap. After testing a few fuses, sometimes you do need to go gradual to see what's going on.

Ed

--- In TekScopes@..., "Craig Sawyers" <c.sawyers@...> wrote:

But like you, I just put the power on and let rip. Never used a variac to
power up stuff, even with the infamous high efficiency power supply in tick
mode on a dummy load.

Craig


 

I agree with Craig and Ed. If there is a capacitor that is ready to fail, I want it to do so now. Reforming old caps is just asking for a future failure and return to the bench. I just us a variac to check regulation specs and then only stuff that goes out for calibration.
 
Low voltage (below spec) on switching power supplies places the maximum stress on everything. That is only ok if you have a source of cheap parts.
 
Regards,
Tom
 
 

----- Original Message -----
Sent: Wednesday, July 17, 2013 12:13 PM
Subject: RE: [TekScopes] Re: Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?

 

> Most electrical and electronic equipment is (or should be) designed to
> withstand any possible line condition, which can include going from
nothing
> to too much, over various time ranges. With linear supplies, the outputs
will
> just be too low and out of regulation if line voltage is too low.
Switching
> supplies usually have UV lockout, so won't start if the line is too low.
Small AC
> motors usually are "impedance protected," while large ones tend to have
> overload protection devices to disconnect a locked rotor fault. Any
> equipment that relies on sequencing or presence of certain internal
supplies
> for proper and safe operation should be designed with appropriate
interlocks
> and protection against this type of failure.

I'd agree for the equipment when new. But (although we don't know what this
equipment is) if this has been in storage for 20 years it is most likely 40
years old or more. So possibly has a few issues.

But like you, I just put the power on and let rip. Never used a variac to
power up stuff, even with the infamous high efficiency power supply in tick
mode on a dummy load.

Craig


 

Hi Tom,


On Wed, Jul 17, 2013 at 6:25 PM, Tom Miller <tmiller11147@...> wrote:
I agree with Craig and Ed. If there is a capacitor that is ready to fail, I want it to do so now. Reforming old caps is just asking for a future failure and return to the bench. I just us a variac to check regulation specs and then only stuff that goes out for calibration.

I believe Conrad Hoffman (who has an excellent website on capacitors
and LCR bridges) said that reforming is a good idea and capacitors can
keep working for many many years after being reformed. Damage due to
powering up a non-reformed capacitor will not break it straight away
unlike you expect it to, it just might mean it'll die in a couple
months, or in ten months. So if anything, reforming would mean *less*
visits to the work bench, at least in the near future...

It's not like capacitors break on their own when just sitting there.
Reforming is just restoring them, not repairing them. The only ways
for a capacitor to die in storage are if it dries out or corrodes or
leaks, and reforming doesn't change any of that. Reforming just
migrates the electrolyte back into the dielectric. If your capacitor
hasn't leaked, then the dielectric should all be there, and if you
reform the capacitor properly it'll be restored to normal function.
It's basically electrolysis.

Low voltage (below spec) on switching power supplies places the maximum stress on everything. That is only ok if you have a source of cheap parts.
That's an interesting detail that I hadn't realized. Puts the whole
reforming idea in new light. Can anyone else confirm this property of
SMPS power supplies?

Cheers,
D.


 

A switching regulated power supply is a constant power device. When the input voltage is low, the current is higher to make the same power. If you go below the rated voltage input, you can exceed the design current of the pass switching devices and overload the magnetics, possibly to saturation.
 
 
 

----- Original Message -----
Sent: Wednesday, July 17, 2013 12:47 PM
Subject: Re: [TekScopes] Re: Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?

 

Hi Tom,

On Wed, Jul 17, 2013 at 6:25 PM, Tom Miller <tmiller11147@...> wrote:
> I agree with Craig and Ed. If there is a capacitor that is ready to fail, I want it to do so now. Reforming old caps is just asking for a future failure and return to the bench. I just us a variac to check regulation specs and then only stuff that goes out for calibration.

I believe Conrad Hoffman (who has an excellent website on capacitors
and LCR bridges) said that reforming is a good idea and capacitors can
keep working for many many years after being reformed. Damage due to
powering up a non-reformed capacitor will not break it straight away
unlike you expect it to, it just might mean it'll die in a couple
months, or in ten months. So if anything, reforming would mean *less*
visits to the work bench, at least in the near future...

It's not like capacitors break on their own when just sitting there.
Reforming is just restoring them, not repairing them. The only ways
for a capacitor to die in storage are if it dries out or corrodes or
leaks, and reforming doesn't change any of that. Reforming just
migrates the electrolyte back into the dielectric. If your capacitor
hasn't leaked, then the dielectric should all be there, and if you
reform the capacitor properly it'll be restored to normal function.
It's basically electrolysis.

> Low voltage (below spec) on switching power supplies places the maximum stress on everything. That is only ok if you have a source of cheap parts.

That's an interesting detail that I hadn't realized. Puts the whole
reforming idea in new light. Can anyone else confirm this property of
SMPS power supplies?

Cheers,
D.


Michael A. Terrell
 

vdonisa wrote:

Wear safety glasses, make sure you can cut off power quickly from a remote switch, have a CO2 fire extinguisher at hand.

Use a momentary foot switch, so the power goes off when you jump back from the flames. :)

http://www.harborfreight.com/momentary-power-foot-switch-96619.html


stefan_trethan
 

Yes. Do not undervoltage no matter what the specification says.
(SMPS designer by day)


You could reform the caps by applying an external voltage with the PS
disabled or out of circuit.

While manufacturer specified shelf life is typically just a couple of
months for electrolytic capacitors actual problems when exceeding it
are rare.

The capacitor will not meet full specification after extended storage,
but in most cases it recovers fast enough at operating voltage so the
stresses stay within the envelope of what the capacitor can take.

ST

On Wed, Jul 17, 2013 at 6:47 PM, cheater00 . <cheater00@...> wrote:

Low voltage (below spec) on switching power supplies places the maximum stress on everything. That is only ok if you have a source of cheap parts.
That's an interesting detail that I hadn't realized. Puts the whole
reforming idea in new light. Can anyone else confirm this property of
SMPS power supplies?

Cheers,
D.


Ed Breya
 

Yes, that's why switchers typically have UV lockout - they would otherwise try to supply the power until the source voltage drops to the point where something burns out, or the circuit stops running.

Ed

--- In TekScopes@..., "Tom Miller" <tmiller11147@...> wrote:

A switching regulated power supply is a constant power device. When the input voltage is low, the current is higher to make the same power. If you go below the rated voltage input, you can exceed the design current of the pass switching devices and overload the magnetics, possibly to saturation.



----- Original Message -----
From: cheater00 .
To: TekScopes@...
Sent: Wednesday, July 17, 2013 12:47 PM
Subject: Re: [TekScopes] Re: Reviving Tek Equipment After 20 Years In Storage...What to Do and Look For?



Hi Tom,

On Wed, Jul 17, 2013 at 6:25 PM, Tom Miller <tmiller11147@...> wrote:
> I agree with Craig and Ed. If there is a capacitor that is ready to fail, I want it to do so now. Reforming old caps is just asking for a future failure and return to the bench. I just us a variac to check regulation specs and then only stuff that goes out for calibration.

I believe Conrad Hoffman (who has an excellent website on capacitors
and LCR bridges) said that reforming is a good idea and capacitors can
keep working for many many years after being reformed. Damage due to
powering up a non-reformed capacitor will not break it straight away
unlike you expect it to, it just might mean it'll die in a couple
months, or in ten months. So if anything, reforming would mean *less*
visits to the work bench, at least in the near future...

It's not like capacitors break on their own when just sitting there.
Reforming is just restoring them, not repairing them. The only ways
for a capacitor to die in storage are if it dries out or corrodes or
leaks, and reforming doesn't change any of that. Reforming just
migrates the electrolyte back into the dielectric. If your capacitor
hasn't leaked, then the dielectric should all be there, and if you
reform the capacitor properly it'll be restored to normal function.
It's basically electrolysis.

> Low voltage (below spec) on switching power supplies places the maximum stress on everything. That is only ok if you have a source of cheap parts.

That's an interesting detail that I hadn't realized. Puts the whole
reforming idea in new light. Can anyone else confirm this property of
SMPS power supplies?

Cheers,
D.


Craig Sawyers <c.sawyers@...>
 

It's not like capacitors break on their own when just sitting there.
They most absolutely do if they are Sprague Twist-Lock capacitors, which
chemically etch through the grounded foil where it meets the case crimp.

Craig


stefan_trethan
 

It's not only that, the rubber seal degrades.
Capacitor manufacturers generally limit endurance predictions at 15
years for that reason.

Modern water based electrolytes (for super low ESR) may limit shelf
life for current instruments due to the more aggressive nature.

ST


On Wed, Jul 17, 2013 at 7:15 PM, Craig Sawyers
<c.sawyers@...> wrote:
They most absolutely do if they are Sprague Twist-Lock capacitors, which
chemically etch through the grounded foil where it meets the case crimp.

Craig


ditter2
 

--- In TekScopes@..., "tubesnthings@..."<tubesnthings@...> wrote:

Sorry, but with regulated supplies there can only be one approach to
power-up: flip the switch. Otherwise you risk exceeding current limits of
psu components. If you're REALLY worried about the electrolytics, reform
them first.
Bernd Schroder
Bernd,

I think you intended to write "witch switching power supplies" rather than "regulated".

- Steve